You must use no-frame version - navigation will be more difficult, but possible.

Use navigation buttons [BACK] [FWD] and browser's History feature. You may also use context menus (right-click) in order to open new documents in new windows and keep current index at hand.
This window will become opened as long as you do not close it.
Each of the links below will open a new index in separate window, however other pages may be opened in the original index's page (depends on the browser's settings).